A Novel Route to Multiphase Polymer Systems Containing Nano-Droplets: Radical Polymerization of Vinylic Monomers in Gelled Water-in-Oil Miniemulsions Christian Holtze, 1 Katharina Landfester, 2 Markus Antonietti* 1 1 Max Planck Institute of Colloids and Interfaces, Research Campus Golm, 14424 Potsdam, Germany E-mail: pape@mpikg-golm.mpg.de 2 Universita ¨t Ulm, Organic Chemistry III – Macromolecular Chemistry and Organic Materials, Albert-Einstein-Allee 11, 89081 Ulm, Germany Received: July 6, 2005; Revised: August 11, 2005; Accepted: August 22, 2005; DOI: 10.1002/mame.200500241 Keywords: composite polymers; gels; inverse emulsion; organo-gelator; (w/o) miniemulsion; photopolymerization Introduction The physico-chemical, mechanical, and electric properties of nanocomposite materials may be substantially different from those of the bulk materials of their individual phases, and will depend on the size of their structuring. This makes them interesting not only for a variety of industrial appli- cations but also for basic science. [1,2] Polymer nanocomposites with a continuous polymer phase are especially promising, as the disperse phase might bring in additional properties to traditional polymer bulk materials and coatings, such as improved mechanical per- formance and scratch resistance for hard filler particles. [3,4] Here, we want to focus on a quite different case, namely polar liquid nanoinclusions, e.g., saline droplets, in dense polymers. It is straightforward to understand that due to the high heat capacity of water and a reversible evaporation/ droplet recovery process, such inclusions would have, for instance, a beneficial influence on the passive preservation of room climate and humidity, thus outperforming current wall coating technology. The controlled release of polar actives from such films, such as drugs, antifouling agents, or antioxidants, is a different application perspective. However, the generation of such a system based on the most simple liquid/liquid approaches did not succeed, up to now. It is an old observation that inverse and bicontinuous microemulsions do not keep their structure throughout the polymerization of the continuous phase and undergo major Summary: A new strategy for the synthesis of composite polymers with larger volume fraction of aqueous inclusions less than 1 mm in diameter is presented. A water-in-oil mini- emulsion of aqueous droplets in a continuous, cross-linkable monomer phase is prepared. The addition of an organo- gelator allows the immobilization of the droplets in a solid gel, thus avoiding the usual demixing upon polymerization of the continuous phase. This pregelled system is then converted into a composite polymer by photoinitiated free radical polymerization. Such coatings may be used for an improved climate control of buildings or as a deposit for the controlled release of actives from polar nano-droplets. SEM image of a cross-linked composite polymer showing controlled droplet inclusions with a maximal diameter of 500 nm. Macromol. Mater. Eng. 2005, 290, 1025–1028 DOI: 10.1002/mame.200500241 ß 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Communication 1025